How can I infinitely loop an iterator in Python, via a generator or other?

Question

It's my understanding that using a Generator is the best way to achieve something like this, but I'm open to suggestions.

Specifically, one use case is this: I'd like to print some items alongside another list, of an arbitrary length, truncating the initial iterator as necessary.

Here is working python code that demonstrates the exact example behavior I desire:

    def loop_list(iterable):         """         Return a Generator that will infinitely repeat the given iterable.          >>> l = loop_list(['sam', 'max'])         >>> for i in range(1, 11):         ...     print i, l.next()         ...          1 sam         2 max         3 sam         4 max         5 sam         6 max         7 sam         8 max         9 sam         10 max          >>> l = loop_list(['sam', 'max'])         >>> for i in range(1, 2):         ...     print i, l.next()         ...          1 sam         """         iterable = tuple(iterable)         l = len(iterable)         num = 0         while num < l:             yield iterable[num]             num += 1             if num >= l:                 num = 0 

The Problem / My Question

As you may have noticed, this only works on lists/tuples/iterables that implement __getitem__ (if I'm not mistaken). Ideally, I'd like to be able to pass any iterable, and receive a generator that can properly loop over it's content.

If there's a better way to do something like this without a generator, I'm fine with that as well.

Answer 1

You can use itertools.cycle (source included on linked page).

import itertools  a = [1, 2, 3]  for element in itertools.cycle(a):     print element  # -> 1 2 3 1 2 3 1 2 3 1 2 3 ...